1. Field of the Present Invention
The present invention relates to a lithographic apparatus and a method for manufacturing a device.
2. Related Art
A lithographic apparatus is a machine that applies a desired pattern onto a substrate or part of a substrate. A lithographic apparatus can be used, for example, in the manufacture of flat panel displays, integrated circuits (ICs) and other devices involving fine structures. In a conventional apparatus, a patterning device, which can be referred to as a mask or a reticle, can be used to generate a circuit pattern corresponding to an individual layer of a flat panel display (or other device). This pattern can be transferred onto all or part of the substrate (e.g., a glass plate), by imaging onto a layer of radiation-sensitive material (e.g., resist) provided on the substrate.
Instead of a circuit pattern, the patterning device can be used to generate other patterns, for example a color filter pattern or a matrix of dots. Instead of a mask, the patterning device can comprise a patterning array that comprises an array of individually controllable elements. The pattern can be changed more quickly and for less cost in such a system compared to a mask-based system.
A flat panel display substrate is typically rectangular in shape. Lithographic apparatus designed to expose a substrate of this type can provide an exposure region that covers a full width of the rectangular substrate, or covers a portion of the width (for example half of the width). The substrate can be scanned underneath the exposure region, while the mask or reticle is synchronously scanned through a beam. In this way, the pattern is transferred to the substrate. If the exposure region covers the full width of the substrate then exposure can be completed with a single scan. If the exposure region covers, for example, half of the width of the substrate, then the substrate can be moved transversely after the first scan, and a further scan is typically performed to expose the remainder of the substrate.
In order to generate devices with ever smaller features, with ever more customization within devices, and in ever more cost-effective ways, there is a continuing drive to improve lithographic methods. However, these three goals often interfere. For example, a new technique can permit the provision of smaller features, but increases the processing time necessary to form the device, thereby increasing the cost of the device. Similarly, a provision of processes that allow greater flexibility in forming the devices can require a compromise in the size of features that can be formed and/or increase the cost of forming a device.
In order to provide an improved process, it has been proposed to provide a lithographic system in which the pattern formed on a substrate is made up of an exposure performed by projecting beams of radiation onto a substrate. The beams interfere in order to provide a repeating, but high resolution, pattern. Exposure of a lower resolution pattern, for example using a patterning device as discussed above, is used in order to “trim” the high resolution repeating pattern to form the desired completed pattern.
Therefore, what is needed is a system and method for controlling the exposure of a substrate by interfering beams of radiation that provide a high resolution repeating pattern.